Polyaryletherketones (PAEKs) are high-performance engineering thermoplastic polymers that possess high temperature stability, excellent electrical insulating properties at high temperatures, good chemical resistance, and high mechanical strength. PAEKs may be amorphous or semi-crystalline, and when burned exhibit low toxicity and corrosive fumes. The materials are of interest for use in biomedical applications such as implant formations as well as the aerospace industry, for instance in interior aviation applications.
PAEKs are characterized by phenylene rings linked via oxygen bridges that include ether and carbonyl (ketone) groups. The ratio and sequence of the ether (“E”) and ketone (“K”) linkages can affect the glass transition temperature and melting point of the thermoplastic polymer as well as the heat resistance and processing temperature. For instance, a polymer possessing a higher ratio of 1,4-phenylene di-ketone linkages (e.g., PEKK) will generally be more rigid and exhibit a higher glass transition temperature and melting point as compared to a polymer possessing a higher ratio of 1,4-phenylene di-ether linkages (e.g., PEEK).
PAEKs are generally formed according to either a nucleophilic aromatic substitution polymerization scheme or an electrophilic aromatic substitution polymerization scheme. Unfortunately, problems exist with both schemes. For instance when utilizing an electrophilic aromatic substitution reaction (e.g., a Friedel-Crafts reaction), the reaction product is prone to precipitation and gelation, particularly at higher conversions, resulting in a large mass of the gelled polymer in the reactor. This material is very difficult to handle and results in increased production costs as well as lower product quality. Typically such a gelled mass has to be finely ground for the subsequent purification processes which are important to remove the catalyst residues and may add to the cost of manufacture of the polymer. Meanwhile, the nucleophilic aromatic substitution reaction requires high temperatures that can promote side reactions and formation of undesired by-products that are difficult to separate from the desired PAEK affecting purity, color, and melt stability of the final product. Furthermore the nucleophilic process involves the use of fluorinated monomers which add to the expense of the product.
As such, a need exists for PAEK formation methods and materials that can produce the polymer in a more suitable particulate form to provide for formation of high purity materials at lower cost circumventing the tedious size reduction grinding processes to facilitate easier and more effective polymer purification.